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500 BCE
the alchemists
Alchemists significantly contributed to the understanding of the atom by laying the groundwork for modern chemistry through their experimental practices, developing basic chemical techniques like distillation and crystallization, and introducing the concept of elements as fundamental building blocks of matter, even though their primary goal was the transmutation of metals, which later led to the idea of rearranging particles within an element to create another -
450 BCE
democritus
Democritus was a central figure in the development of the atomic theory of the universe. He theorized that all material bodies are made up of indivisibly small atoms. Aristotle famously rejected atomism in On Generation. Democritus' atomic theory states that all matter is composed of tiny, indivisible particles called "atoms" which are constantly moving through empty space, and the different properties of matter arise from the varying shapes and sizes of these atoms -
427 BCE
plato
Plato's most famous work is the Republic, which details a wise society run by a philosopher. He is also famous for his dialogues, which shows his metaphysical theory of forms -
384 BCE
artistotle
Aristotle was an Ancient Greek philosopher and polymath. His writings cover a broad range of subjects spanning the natural sciences, philosophy, linguistics, economics, politics, psychology, and the arts. Aristotle is best known for founding the field of formal logic in the West -
robert boyle
Developing the experimental method in chemistry and proposing an early atomic theory through his corpuscular theory detailed in his book The Sceptical Chymist. -
john dalton
John Dalton is best known for his pioneering theory of atomism. The theory of atomism, proposed by Dalton in the early 19th century and derived from meteorological studies, is the foundation for our modern concept of the atom. -
newlands law of octaves
law of octaves, in chemistry, the generalization made by the English chemist J.A.R. Newlands in 1865 that, if the chemical elements are arranged according to increasing atomic weight, those with similar physical and chemical properties occur after each interval of seven elements. -
discovery of radioactivity
Henri Becquerel discovered radioactivity in 1896 while investigating uranium salts and X-rays -
Robert Millikan
Robert Millikan's accomplishments were the design and fine-tuning of experiments which unambiguously confirmed the most important scientific theories of his time, providing the implications for atomic theory. His oil drop experiment confirmed the existence of the electron and accurately determined its charge. -
rutherfords gold foil experiment
A piece of gold foil was hit with alpha particles, which have a positive charge. Most alpha particles went right through. This showed that the gold atoms were mostly empty space. -
plancks quantum theory of light
Planck's quantum theory of light states that light is not emitted or absorbed as a continuous wave, but rather in discrete packets of energy called quanta or photons, where the energy of each photon is directly proportional to its frequency, a concept that helped explain the phenomenon of blackbody radiation and laid the foundation for quantum mechanics; essentially, light behaves like particles in addition to waves, exhibiting wave particle duality. -
bohrs planetary model
the Bohr model, often referred to as a planetary model, the electrons encircle the nucleus of the atom in specific allowable paths called orbits. When the electron is in one of these orbits, its energy is fixed. -
Plum pudding model
It was first proposed by J. J. Thomson in 1904.
In Thomson's plum pudding model of the atom, the electrons were embedded in a uniform sphere of positive charge, like blueberries stuck into a muffin. -
mosleys atomic numbers
Moseley's atomic numbers refer to the concept that the atomic number of an element is the number of positive charges in its nucleus, which is now understood to be the number of protons. -
discovery of the proton
The discovery of the proton is credited to Ernest Rutherford. Based on the conclusions drawn from the gold-foil experiment -
heisenburge uncertainty principle
German physicist Werner Heisenberg, that the position and the velocity of an object cannot both be measured exactly, at the same time, even in theory. -
photoelectric effect
German physicist Heinrich Hertz, When light shines on a metal, electrons can be ejected from the surface of the metal -
mendeleevs pd table
Mendeleev's periodic table has 6 horizontal rows called periods and 8 vertical rows called groups. The groups 1 to 7 had two sub groups called A sub group and B sub group. Group 8 had 3 rows of elements. Elements having similar properties were placed in the same groups. -
schrodinger equation
Essentially a wave equation, the Schrödinger equation describes the form of the probability waves. -
discovery of the neutron
British physicist James Chadwick discovered the neutron, a neutral particle with a mass similar to a proton